Among servomotors and control devices used in various prime movers such as a gas turbine and a steam turbine, some of the known types are hydraulically controlled. A hydraulic device used for the hydraulic control includes a low-pressure oil channel for supplying low-pressure oil which is to be used as lubricant oil for a bearing or the like of a turbine and a high-pressure oil channel for supplying high-pressure oil which is to be used in the hydraulic control of a servomotor, a control device, or the like. As such a hydraulic device, Patent Literature 1 discloses a hydraulic device which is capable of supplying oil discharged from a supply pump to a high-pressure oil channel, as well as accumulating pressure of the high-pressure oil channel in an accumulator when, for instance, the supply pump is stopped.